But I see that you had a custom-animation for a modal, so just wanted to share my experience:

I asked my self the same question, because I had a customized modal, I spend one or two hours or something of research about how to do a custom animation and how to custom style my modal, but finally I decided to just give up on my custom modal and replaced it for a Popover in v4

So like I said maybe not an answer directly, but maybe you could replace your custom modal with a popover too?